1. Field of the Invention
The invention relates to a vibration sensor for monitoring the state of rotating components or bearings, with a sensor element, with evaluation electronics and with at least one interface. In addition the invention also relates to a process for monitoring the state of rotating components or bearings with a vibration sensor which has a sensor element and evaluation electronics.
2. Description of Related Art
In mechanical engineering and plant engineering there are a host of machines and systems which each have rotating components, generally a shaft. The shaft is supported via a bearing, especially a roller bearing, in the stationary housing of the machine or equipment. Depending on the embodiment, the inside ring or the outside ring of the bearing being movably arranged, while then accordingly the inside ring or the outside ring is supported to be stationary. Problem-free serviceability of the bearing, as the force-transmitting component in motion, is decisive for the serviceability of the machine or system. Due to high dynamic and static loads in operation and as a result of structural limitations, the bearing often constitutes the “Achilles heel” of the machine or system. Thus, bearing defects are by far the most frequent cause of failure for electrical drives.
For this reason, there are a host of various sensors and methods for monitoring the state and for detection of bearing damage. In addition to measuring the temperature of the bearing and analyzing the bearing lubricants, especially of the bearing oil, mainly vibration-diagnostic methods are used to assess the state of the bearing. Using an acceleration sensor, the solid-borne noise signal of the bearing which is to be monitored on the machine surface is detected and analyzed. In doing so, however, simple characteristic values of the vibration signal, such as the effective value, the peak value or the quantitative average, do not allow reliable conclusions about the state of the monitored bearing. In particular, for early detection of damage, these characteristic values are completely unsuited. This is also due especially to complex operating conditions and to the host of bearings, which can be used, and which are used with their different dimensions and characteristic values.
Reliable early diagnoses of bearing damage or unbalanced masses of rotating components is therefore only possible with comprehensive evaluation of the high frequency signals delivered by the vibration sensor in the range up to a few kilohertz. The evaluation of these high frequency signals generally takes place using spectral signal analysis. In this way, it is not only possible to draw a conclusion regarding whether a bearing is intact or damaged, but a conclusion can also be drawn about the type of damage. Likewise a conclusion can be drawn about the expected remaining service life of the bearing. Although it is thus possible by measurement engineering to detect varied damage early, vibration sensors for monitoring the state of rotating components or bearings are used only rarely in practice.
The prior art in industrial monitoring of bearings is limited, on the one hand, to intermittent measurement with hand measuring instruments, and on the other hand, to the use of relatively expensive central measurement systems, which as a result of high procurement costs are feasible only for monitoring of high-value machines, such as turbines or large gear trains. Intermittent measurement with hand measuring instruments has the disadvantage that continuous checking of the state of the bearing does not take place, so that reliable early diagnosis of damage is not possible. Moreover, as a result of the different operating conditions, it is only possible with difficulty to draw a reliable conclusion about the state of the bearing from the different measured values. To do this, the corresponding expert know-how is necessary, resulting in high personnel expenditure and high costs.
In the implementation of a central measurement system, as a result of the large number of data to be evaluated, on the one hand, the cabling of the individual vibration sensors to the central data processing systems is complex, and on the other hand, due to the real time capacity, which is often required, very high demands are imposed on the central data processing system. In this case, the central data processing system for reasons of safety in addition is often having to be made redundant. But even with the use of a correspondingly powerful and high-speed data processing system, due to the large number of data to be evaluated, the number of sensors, which can be connected to the data processing system, is very limited, if the individual sensors are to be evaluated in real time and not only in a multiplexed process. Because the individual sensors must be connected to the central data processing system via separate lines, such a central measurement system has an expansion capacity, which is made very limited or has none at all. Thus, planning of a central measurement system requires thorough preparation, and machines and sensors, which may have to be added at a later time, having to be taken into account at the same time in the planning.